The objectives of this proposal are: 1) to define the proliferative and functional characteristics of normal and malignant human hematopoietic cells; 2) to delineate the mechanisms controlling human granulopoiesis; 3) to fractionate human bone marrow with the aim of providing hematopoietic reconstitution in bone marrow failure and neoplastic diseases; and 4) to utilize information obtained from in vitro cultures of human bone marrow for the treatment of malignant disease.